Epoxide resin compositions



United States Patent 3,021,304 EPOXIDE RESIN COMPOSITIONS Sylvan Owen Greenlee, Racine, Wis., assignor to Devoe & Raynolds Company, Inc., Louisville, Ky., a corporation of New York No Drawing. Filed Aug. 5, 1954, Ser. No. 448,157 4 Claims. (Cl. 260-47) This invention relates to epoxide resin compositions which are valuable compositions for use in the manufacture of infusible, insoluble products. The invention includes the new compositions, and the method of making infusible products therefrom.

The new compositions include a polyhydric phenol having three or more hydroxyl groups and an epoxide resin resulting from the reaction of a mixture of a dihydric phenol with epichlorhydrin or glycerol dichlorhydrin and sufiicient caustic alkali to combine with the chlorine of the chlorhydrin, the proportion of chlorhydrin (epichlorhydrin or glycerol dichlorhydrin) to dihydric phenol being at least about 1.2 to 1 and up to around 2 to 1.

The invention also includes a two step method of forming infusible insoluble products in which an initial low molecular weight or melting point epoxide resin is first produced by the reaction of a dihydric phenol with an excess of epichlorhydrin or glycerol dichlorhydrin in the presence of caustic alkali sufiicient to combine with the chlorine of the chlorhydrin, followed by removal of the byproduct salt and any excess alkali from the initial epoxide resin, with addition of a polyhydric phenol containing more than two phenolic hydroxyl groups to the initial epoxide resin and heating the resulting mixture to effect reaction of the polyhydric phenol with the epoxide resin to form insoluble and infusible reaction products.

In the first step of the two step process, low molecular weight or melting point epoxide resins are produced which can be readily washed free from byproduct salt and any excess caustic alkali. When the low melting point or low molecular weight epoxide resins are further reacted with the trihydric or higher polyhydric phenol in the second step of the process, no byproducts are formed, and the reaction is a direct reaction of addition between the epoxide resin and the added polyhydric phenol in the second step of the process.

The polyhydric phenols used for reaction with the epoxide resins to form the infusible, insoluble phenol reaction products include trihydric phenols and higher polyhydric phenols. Trihydric phenols are trifunctional and, when used in suitable proportions, form compositions with the epoxide resins which readily are convertible, either without or with the presence of a catalyst such as an alkaline catalyst, to infusible insoluble products. Polyhydric phenols containing more than three phenolic hydroxyl groups give more complex reaction in crosslinking the epoxide resins. The polyhydric phenols having more than two phenolic hydroxyl groups may contain the hydroxyl group in one nucleus, as in pyrogallol and phloroglucinol, or in different nuclei of fused ring systems, such as polyhydroxy naphthalenes, or in difierent nuclei or ring systems attached by chains composed of one or more atoms, such as o,p,o',p'-tetrahydroxy diphenyl dimethyl methane and other polyhydroxy diphenyl or clinaphthyl methanes, etc.

The proportions of polyhydric phenol containing more than three phenolic hydroxyl groups and of epoxide resins can be varied. The proportions can thus vary from less than equivalent proportions, considering one phenolic hydroxyl of the polyhydric phenol as equivalent to one epoxide group of the resin, to more than equivalent proportions. Proportions can thus be used which are equivalent or where the phenolic hydroxyl is only about "ice one half that equivalent to the epoxide group of the resin, or where an excess of e.g. one and one-third phenolic hydroxyl to one epoxide group of the resin is used.

The epoxide resins which are used with the higher polyhydric phenols in making the new compositions are resins which result from the reaction of dihydric phenols and chlorhydrins such as epichlorhydrin and glycerol dichlorhydrin. In making these resins, the proportions of dihydric phenols and chlorhydrins are such that substantially more than 1 molecular proportion of a difunctional chlorhydrin is used for 1 molecular proportion of dihydric phenol, and 2 or substantially less than 2 molecular proportions of the difunctional chlorhydrin are used for 1 molecular proportion of the dihydric phenol. Similarly with other polyhydric phenols and other polyfunctional chlorhydrins, the proportions are such that the halohydrin is more than that which is equivalent to the polyhydric phenol and twice or less than twice the equivalent amount.

In making the epoxide resins from chlorhydrins, the reaction of the polyhydric phenols and the chlorhydrins is advantageously carried out with the use of aqueous alkali in amount sufiicient to combine with the chlorine of the chlorhydrins used, or in amount somewhat in excess, as, vwhere the dihydric phenol is reacted with an epihalohydrin such as epichlorhydrin, the proportion of alkali used is suflicient to combine with the chlorine of the epichlorhydrin or an amount somewhat in excess of that amount. When a dihalohydrin such as glycerol dichlorhydrin is used, the amount of alkali is sufficient to combine with the chlorine of the dichlorhydrin, or an amount somewhat in excess of that amount. And when mixtures of epichlorhydrin and dichlorhydrin are used, the amount of alkali is similarly sufiicient to combine with the chlorine or somewhat in excess of that amount.

The epoxide resins vary somewhat in their compositions and properties depending upon the dihydric phenols and chlorhydrins used and the conditions of the reaction.

The primary reaction involved in producing the epoxide resins from dihydric phenols and difunctional chlorhydrins, appears to be one in which the phenolic hydroxyls react with the chlorhydrins to give monomeric and straight chain polymeric products such as illustrated by the following formulas or structures:

where R is the residue of a dihydric phenol, R is an intermediate hydroxyl-containing residue of the chlorhydrin or dichlorhydrin, and R is mainly an epoxy-containing residue and to some extent a hydroxyl-containing residue derived from the chlorhydrin. In the above formula, n represents the extent of polymerization, e.g. 1, etc.

In general the proportion of terminal epoxide residues or groups in the epoxide resin is in considerable excess of the terminal hydroxide-containing residues, so that the products approch diepoxides, e.g., diglycidyl ethers and polymeric ethers of the dihydric phenols.

The above formula of the polymeric epoxide resins assumes straight chain reaction which appears to be the primary reaction between the dihydric phenols and epichlorhydrin or dichlorhydrin. Reaction is not, however, excluded between the halohydrin and intermediate a1- coholic hydroxyl'groups such as would give branch chain formulas; and in the case of more complex polymers, where n in the above formula is higher than 1, such side chain reaction products and polydimensional polymers are probably formed to some extent either by reaction of intermediate hydroxyl groups of intermediate reaction products with the halohydrin or with terminal epoxy groups of other intermediate reaction products. Since terminal epoxy groups can also react with terminal hydroxyl groups, it may be that part of the polymerization takes place in this way.

It is diificul-t to determine the exact nature of the complex polymerization process which takes place, but I am led to believe that the reaction is primarily one between the phenolic hydroxyls and the chlorhydrins and to a limited extent one of reaction of halohydrins or epoxide groups with aliphatic hydroxyl groups, and that the resulting complex hydroxy-epoxy compositions are largely straight-chain polymeric products of the formula indicated above and to some extent more complex polydimensional structures. a

The epoxide resins vary from liquid or semi-solid products to solid resins.

The polyhydric phenols used in making the intermediate epoxide resins may contain the hydroxyl groups in one nucleus as in resorcinol or in different nuclei of fused ring systems as in 1,5-dihydroxynaphthalene or in dififerent, nuclei or ring systems attached by chains composed of one or more atoms, in which case the chains should be free from elements which interfere with the reaction of chlorhydrins with the phenolic hydroxyl groups. The phenolic nuclei or the chains linking phenolic nuclei may contain substituents provided they do not interfere with the desired reaction of the chlorhydrins with the phenolic hydroxyl groups. Illustrative of polyhydric phenols which may be used in making the new complex polymerization products are mononuclear phenols such as resorcinol, hydroquinone,'catechol, phluorglucinol, etc. and polynuclear phenols such as bisphenol (p,p'-dihydroxydiphenyldimethyl methane), p,p'-dihydroxybenzophenone, p,p'-dihydroxydiphenyl, p,p'-dihydroxydibenzyl, bis-(4-hydroxyphenyl) sulfone, 2,2'-dihydroxy 1,l'-dinaphthyl methane, polyhydroxy naphthalenes and anthracenes, o,p,o,p'-tetrahydroxy diphenyl dimethyl methane and other dihydroxy or polyhydroxy diphenyl or dinaphthyl methanes, etc.

A particularly advantageous polyhydric phenol for use in making the new compositions is bisphenol (p,p-dihydroxydiphenyldimethyl methane).

The difunctional or polyfunctional chlorhydrins useful in making the initial epoxide resins include monochlor- 'hydrins such as epichlorhydrin, dich-lorhydrins such as glycerol dichlorhydrin, bis(3-chloro-2-hydroxy propyl) ether, 1,4-dichloro, 2,3-dihydroxy-butane, 2-methyl-2- hydroxy, 1,3-dichloropropane, bis(3-chloro, Z-methyl, 2- hydroxy propyl) ether and other mono and dichlorhydrins derived from aliphatic olefins, mannitol, sorbitol and other alcohols. Epichlorhydrin is particularly advantageous for use in making the initial resins in the first step of the process.

In making the epoxide resins from chlorhydrins, the dihydric phenols, e.g., bisphenol, and the polyfunctional chlorhydrins are advantageously all added together at the outset together with aqueous alkali which may be used to dissolve or partly dissolve the polyhydric phenol to form the polyphenoxide or a monophenoxide either before admixture with the chlorhydrin or after admixture. The amount of caustic alkali added to dissolve or partially dissolve the phenol, and whether present at the outset or added in successive amounts, should be suificient to combine with the chlorine of the chlorhydrin used. With epichlorhydrin, for example, the amount of caustic alkali should be equal to or somewhat in excess of the theoretical amount for combining with the chlorine of the epichlorhydrin. With glycerol dichlorhydrin 2 mols of caustic alkali or somewhat more are required for 1 mol of the dichlorhydrin. The presence of an excess of alkali is advantageous in securing completion of'the reaction, and also influences the polymerization and the nature of the polymerization products as Well as the relative proportions of epoxide groups and terminal hydroxy-containing groups.

Products of a predetermined degree of polymerization and of diflerent degrees of polymerization can be obtained by regulating the proportions of the reactants used.

Thus, to give a composition having the general or approximate composition indicated by the above formula where n=l the proportions of epichlorhydrin and bisphenol should be about 3:2. Products of higher degree of polymerization and increased complexity of composition are obtained with lower ratios of epichlorhydrin to bisphenol. For example, a product made from 5 mols of epichlorhydrin and 4 mols of bisphenol would have a theoretical composition approximating that of the above formula where n=3. A low molecular weight resin varying from a liquid to a soft solid and with a large proportion of liquid monomeric polyethers of dihydric phenols can be made by reacting 2 mols of epichlorhydrin with 1 mol of bisphenol. Yields of products can be obtained which represent or approximate the theoretical yields indicating that the complex polymerization products contain the phenolic and halohydrin residues in substantially the same proportion in which the reactants are used.

The range of proportions and degree of polymerization in making the resins can be varied over a considerable range, but the chlorhydrin should be in substantial excess of the equivalent proportions to insure terminal epoxycontaining groups and should be twice or less than twice the equivalent proportions. The production of the polymeric products requires in general, in the caseof a dihydric phenol and epichlorhydrin or dichlorhydrin, a range of proportions varying from about 2 of the polyhydric phenol and 3 of the difunctional chlorhydrin to a higher proportion of polyhydric phenol to chlorhydrin approaching equivalent proportions but with suificient excess of the chlorhydrin over equivalent proportions so that the complex polymeric products will contain terminal epoxide groups. With bisphenol and epichlorhydrin ranges of proportions corresponding to that of the above formula where n is from 1 to 5 are particularly advantageous, giving complex reaction products having a melting point up to around C. or higher and from which the salt formed as a by-product and any excess caustic may be removed by washing.

Higher polymeric products of higher melting point which cannot be readily washed to remove salt or any excess caustic canadvantageously be produced by the two-step process in which a lower melting polymeric product is first formed which can be readily freed from by-product salt and excess caustic, and with further reaction of this intermediate purified product with an additional amount of dihydric phenol which is less than the equivalent of the epoxide groupsto the intermediate product so that the higher polymeric products will still contain epoxy groups.

The process which can be advantageously used in preparing the initial epoxide resins will be illustrated in connection with the reaction of bisphenol with epichlorhydrin.

A caustic soda solution is made containing 1 mol caustic soda per mol of bisphenol dissolved in an amount of water, e.g., twice that of the weight of the bisphenol to be used. The bisphenol is then added to the caustic solution in a suitable reaction kettle provided with a stirrer and stirred until the phenol is dissolved. The use of this amount of alkali is sufficient to convert only half of the phenolic hydroxyls of the bisphenol into phenoxide. 'Ihe epichlorhydrin is then added to the solution at a temperature of 34-45" C. with continuous agitation of the reaction mixture. The temperature rises over a period of e.g., 30 minutes to around 60-75 C. depending upon the initial temperature, the batch size and the amount of a water used, larger amounts of water tending to control the exothermic reaction temperature. The temperature rise due to the exothermic reaction can be controlled to some extent by using larger or smaller amounts of Water.

After this preliminary reaction an additional amount of sodium hydroxide conveniently in water solution, and sufiicient in amount, with that previously added, to react completely with the chlorine of the epichlorhydrin, is

added, and heat is applied if necessary to raise the temperature to around 80-85 C. over a period of around -20 minutes. A further amount of sodium hydroxide in water is advantageously added at this point, in excess of the theoretical amount required to react with all of the chlorine present in the epichlorhydrin, and this amount may advantageously be an appreciable excess of caustic soda to secure a higher degree of polymerization in the reaction mixture or to bring the reaction to the desired extent in a shorter period of time. The mixture is heated to around 95 C. and held at around 95-100" C. for a sufiicient length of time to give the desired products which may vary e.g. from /2 hour to 3 hours or more.

The reaction mixture separates into an upper aqueous layer which is drawn OE and the residue, e.g., of tafiy-like consistency settles to the bottom. This product is then washed by stirring with hot water for -30 minutes after which the wash water is drawn off. This washing procedure is repeated e.g., 4 to 6 times, or as many times as is necessary, to effect removal of any unreacted sodium hydroxide and the byproduct sodium chloride. Dilute acids such as acetic or hydrochioric acid may be used to neutralize the excess caustic during washing. It is usually desirable to wash the product entirely free from salt and caustic since failure to remove the unreacted caustic or basic salts such as sodium acetate may result in further polymerization during the drying process when heat is applied to remove the last traces of water. The wet resin is dried by heating and stirring until the temperature rises substantially above the boiling point of water.

The above procedure has been found an advantageous procedure for use in producing the initial epoxide resins. The addition of alkali in stages and with only partial conversionof bisphenol into phenoxide in the first stage results in reaction of the bisphenol with part of the epichlorhydrin and the removal of chlorine from only part of the epichlorhydrin while part of the phenolic hydroxyls of the bisphenol are left in a free state such that they are free to react with epoxide groups. The subsequent addition of caustic is sufiicient to remove chlorine from the remaining epichlorhydrin in the further carrying out of the process while the use of a regulated excess of alkali over that required for combining with the chlorine to form salt aids in promoting and controlling the further carrying out of the process.

Where all of the caustic alkali is added at the beginning of the process and all of the reactants are added the reaction is more exothermic and temperature control may be necessary by external cooling or the addition of ice or cold Water to keep the reaction under control. Excessive amounts of caustic sometimes causes further polymerization so that it becomes difficult to control the melting point of the product. Lesser amounts of excess caustic approaching the theoretical require longer reaction periods for the process. In general the process should be controlled so that the reaction product does not have a melting point more than 10-15 higher than the temperature of the water used for washing. Thus a product having a softening point or melting point (Durrans Mercury Method) of around 60 C. may be prepared and washed at a temperature above e.g., 4550 C. A product whose softening point is around 125 C. may be prepared and washed in a closed pressure kettle at temperatures above 110-115 C.

A typical example illustrative of the process in which approximately 3 mols of bisphenol is reacted with 4 mols of epichlorhydrin and an amount of sodium hydroxide approximately 25% in excess of the theoretical is carried out as follows: The ingredients used were as follows: 3075 pounds bisphenol, 166.3 pounds epichlorhydrin, 96 pounds caustic soda, 600 pounds water. 54 pounds of the caustic were dissolved in 600 pounds of water in an open kettle provided with a mecham'cal agitator. The bisphenol was added and the mixture stirred for about 10 minutes at a temperature of about 33 C.,

the epichlorhydrin was added and the temperature increased to about 65 C. from the exothermic heat of reaction. A solution of 18 pounds of caustic soda dissolved in 4 gallons of water was then added with continued stirring with a rise of temperature to around 79 C. Heat was applied to raise the temperature to about 85 C. and a solution of 24 pounds of caustic soda dissolved in 5 gallons of water was added and heating continued while maintaining a temperature around 90 to 100 C. for a period of about 1 hour. External heating was discontinued, 5 gallons of cold water added to check boiling of the water and the upper aqueous layer was then drawn off.

The product was washed with 5060 gallons of boiling water for a period of 20 minutes, then with a similar amount of boiling water containing acetic acid to neutralize unreacted caustic soda and then 4 times in succession with a similar amount of boiling water. After as much as possible of the water had been removed, external heat was applied with continued stirring to dry the product, the temperature rising to 150 C. The liquid product was drawn off and allowed to solidify, and had a softening point of 95 C. (Durr-ans Mercury Method).

Higher melting point products which cannot be readily washed with water may advantageously be prepared by proceeding in two steps. Thus where products are desired having a melting point of, e.g., around 150 C., such that they cannot be readily freed from salt and excess caustic by washing, they can advantageously be produced by a two step procedure. While such a product, if prepared by the above process, could be washed in a pressure kettle with water heated to around l45l50 C., this requires special pressure equipment. The use of such high pressures and temperatures is avoided when the following two step procedure is used.

In this two step procedure an epoxide-containing product is first produced which melts e.g. at C. Such a.

product can be easily prepared at temperatures above 65- 70 C. and washed with hot Water at atmospheric pressure in an open or closed kettle. This product, free from caustic, water and salts, is then admixed with an additional amount of polyhydric phenol, less than that corresponding to the epoxy content of the product with which it is admixed, and the mixture then heated to effect the action of the polyhydric phenol with part of the epoxy groups of the initial product to give an epoxide resin that melts e.g. at C. and which needs no purification since no byproducts are formed in this second step of the process.

In some cases it is desirable, in the second step of the two step process of producing higher melting point epoxide resins, to add traces of catalysts such as sodium hydroxide or sodium acetate, to catalyze the further reaction to produce the higher melting epoxide products, but these catalytic substances are used in such small quantities that they are not detrimental to the product for most of its uses, and their removal by washing or other methods is unnecessary.

In order to regulate the amount of dihydric phenol which is added to the low melting point resin to produce a higher melting point epoxide resin, the epoxide equivalent of the initial epoxide resin is determined, as hereinafter described, and an amount of dihydric phenol is added which is less than that equivalent to the epoxide content so that only part of the epoxide groups of the complex composition are utilized in forming the further polymeric product, and leaving an excess of epoxide content of the resulting product such that it is still an epoxyhydroxy product, still capable of reaction e.g. by polymerization with the addition of a polymerization catalyst,

or cross-linking reactant.

The epoxide resins which are to be further reacted with the trihydric and higher polyhydric phenols can also he produced by a two-step process in which an excess of '2 dihydric phenol is reacted with less than the equivalent of epichlorhydrin and caustic alkali to produce a complex dihydric phenol which is further reacted with an excess of epichlorhydrinaud caustic alkali'to form the epoxide resin, or which is further reacted with an excess of epoxide resin to form a higher melting point resin.

The epoxide resins, whether those initially produced by a one-step process, or of higher melting point produced by further reaction of the resins first produced to form higher melting point epoxide resins, are used in admixture with additional trihydric or higher polyhydric phenol in making the new compositions.

With trihydric and higher polyhydric phenols used with the'epoxide resins, equivalent proportions may be used with advantage, so that, for example, the number of phenolic hydroxyls of the trihydric phenol is approximately equivalent to the number of epoxide groups of the epoxide resin, or less than equivalent proportions, since the trihydric and higher polyhydric phenols are poly functional in character and can serve to cross-link the epoxide resins to give infusible, insoluble products even where less than the equivalent amount of trihydric phenol'is used. The proportions may thus vary from half the equivalent amount of polyhydric phenol to more than the equivalent amount, e.g., one and one-third times the equivalent amount.

The nature and advantages of the invention will be further illustrated by the following specific examples, but it will be understood that the invention is not limited thereto. The parts are by weight.

The epoxide group content of the epoxide resins, both those initially produced and the more complex higher melting point epoxide resins produced by the two step process, was determined for practical purposes by determining the equivalent weight of the composition per epoxide group. The method used for determining the epoxide content of the epoxide resins hereinafter indicated was by heating one gram sample of the epoxide composition with an excess of pyridine containing pyridine hydrochloride (made by adding 16 cc. of concentrated hydrochloric acid per liter of pyridine) at the boiling point for 20 minutes and back titrating the excess pyridine hydrochloride with 0.1 N sodium hydroxide using phenolphthalein as indicator, and considering that 1 HCl is equivalent to one epoxide group.

Example 1 illustrates the production of an epoxide resin suitable for reaction with a polyhydric phenol.

Example 1.798 parts of bisphenol were dissolved in a caustic soda solution made by dissolving 200 parts of caustic soda in 1730 parts of water in a stainless steel kettle, and 650 parts of epichlorhydrin were added to. the closed kettle. The kettle was provided with a stirrer and the mixture was stirred during the process. The temperature rose from around 37 C. to around 70 C. in about 45 minutes. 80 parts of caustic soda in 200 parts of water were then added with further increase in temperature to about 82 C. in about one-half hour. 29 parts of caustic soda in 100 parts of water were then added and the kettle was heated to raise the temperature gradually to about 95 C. in about one hour. The aqueous liquor was then drawn ofi and hot wash water applied withagitation, and a series of four washing treatments with fresh water was applied until the product became neutral to litmus. The product was then dried by heating to a final temperature of 130 C., and drawn from the kettle. V

In the above example, 2 mols of epichlorhydrin are used for 1 mol of bisphenol with an amount of caustic soda somewhat in excess of 2 mols. The softening point of the resulting resinous product determined by Durrans Mercury Method was 43 C. The approximate molecular weight determined by a standard boiling point elevation.

method was about 451. The determination of the epoxide groups, in the product showed an equivalent weight of 325 per epoxide group which would represent approximately 1.39 epoxy groups per molecule of the average molecular weight indicated, and an equivalent weight to esterification of 8415.

While the'product is a homogeneous product, it is a composite product made up of monomeric and polymeric epoxide ethers of bisphenol. By fractional extraction with normal heptane a liquid fraction is obtained, leaving a higher melting point resin. By fractional distillation at 1 micron pressure and between 160 C. and 300 C. approximately half the material distilled and a large part of this distillate was liquid and apparently made up largely of diglycide ether of bisphenol with some hydrolyzed epoxide and some polymeric product. Fractions were thus obtained having an epoxide equivalent of 183 to 184 and fractions having somewhat higher epoxide equivalents up to around 300. The residual resin had a melting point of about 625 C. and an epoxide equivalent of about 525. In referring to average molecular weight based on a standard boiling point elevation metho'cl, accordingly, and epoxide groups per molecule based on the average molecular weight, these figures do not represent a homogeneous, uniform product but a mixture of monomeric and polymeric liquid and solid resins including diepoxides and polymeric and hydrolyzed products.

The following example illustrates the reaction of the resin of Example 1 with the higher polyhydric phenol having more than two phenolic hydroxyl groups. Example 2.The resin of Example l was further reacted'by adding 42 parts of phloroglucinol to 325 parts of resin, corresponding to an equivalent of about one phenolic hydroxyl 'per epoxide group, and this mixture was heated for minutes at 200 C(and gave an infusible product.

Example 3.0.87 part of phloroglucinol (0.021 mol of phenolic OH), a trihydric phenol, was dissolved in 20 parts of the resin produced from bisphenol, epichlorhydrin and caustic alkali and having a melting point of 98 C. and an epoxide equivalent of 948 (0.021 mol of epoxide). This solution, when heated to 200 C. for 1 hour, gave a hard, extremely tough, infusible product.

Example 4.0.65 part of phloroglucinol (0.0158 mol of phenolic OH) was dissolved in 20 parts of the epoxide resin of Example 3 (0.021 mol of epoxide). This represents 75% of the equivalent amount of phenolic OH to epoxide groups. The solution was heated at 200 C. for 1 /2 hours to give a hard, tough, infusible product.

Example 5.-0.44 part of phloroglucinol (0.011 mol ofphenolic OH) was dissolved in 20 parts of the same resin used in Example 3 (0.021 mol of epoxide). The solution was heated at 200 C. for 3 hours to give a rubbery gel. When cold, the product was a hard, brittle solid.

Example 6.Example 3 was repeated using pyrogallol in place of phloroglucinol. The product was a hard, extremely tough, infusible product.

. Example 7.-Exam-ple 4 was repeated using pyrogallol in place of phloroglucinol. The product was a hard, tough, infusible product.

Example 8.-4 parts of phloroglucinol (0.098 mol of phenolic hydroxyl) was dissolved in 20 parts of a resin which was a technical grade diglycid ether of bisphenol having an epoxide equivalent of 202 (0.099 mol of epoxide). This solution was heated for 30 min. at 200 C. to give a hard, tough, infusible product.

Example 9.4 parts of pyrogallol (0.098 mol of phenolic hydroxyl) was dissolved in 20 parts of technical grade diglycid ether of bisphenol having an epoxide equivalent of202 (0.099 mol of epoxide). This solution was heated to 200 C. for 1 /2 hours to give a hard infiusible product.

A more rapid reaction takes place if 1% sodium phenoxide is added to the solution. With the addition of this catalyst a hard, tough, infusible product is formed in30 minutes at C.

Example 10.5.45 parts of pyrogallol (0.13 mol of phenolic hydroxyl) was dissolved in 20 parts of the diglycide ether used in the preceding example (0.099 mol of epoxide). This solution also gave a hard, infusible product when heated for 1 /2 hours at 200 C.

The addition of 1% sodium phenoxide also makes this reaction take place more rapidly at a lower temperature.

Example 11.The epoxide resin used in this example was one produced from bisphenol, epichlorohydrin and sodium hydroxide having a melting point of 50 C. and an epoxide equivalent of 348. 2.42 parts of phloroglycinol (0.0575 mol of phenolic hydroxyl) was dissolved in 20 parts (0.0575 mol of epoxide) of the above resin, and the solution was placed in an oven at 200 C. After 30 minutes the solution gelled and in 1 /2 hours a hard, tough, infusible product was formed.

Example 12.A solution of 20 parts (0.0575 mol of epoxide) of the epoxide resin used in the preceding example and 3.22 parts (0.0767 mol of phenolic hydroxyl) of phloroglucinol was placed in an oven at 200 C. The solution gelled in 30 minutes and formed a hard, tough, infusible product in 1 /2 hours.

Example 13.-The epoxide resin used in this example was one produced from bisphenol, epichlorohydrin and sodium hydroxide having a melting point of 82 C. and an epoxide equivalent of 586. 1.43 parts of pyrogallol (0.0342 mol of phenolic hydroxyl) was dissolved in 20 parts of the above resin (0.0342 mol of epoxide). The solution was placed in an oven at 200 C. After 30 minutes the solution gelled and after 1 /2 hours a hard, tough, infusible product was formed.

Example 14.-A solution of 20 parts of the epoxide resin (0.0342 mol of epoxide) used in the preceding example and 1.91 parts of pyrogallol (0.0455 mol of pheenolic hydroxyl) was placed in an oven at 200 C. The solution gelled in 45 minutes and after 1 /2 hours a hard, tough, infusible product was formed.

Other trihydric, tetrahydric and other polyhydric phenols containing more than two phenolic hydroxyl groups can similarly be used.

The trihydric and higher polyhydric phenols differ from the dihydric phenols in their reaction, with the epoxide resins, in that they are trifunctional or higher and can react by cross-linking between three or more dififerent epoxide molecules; while the dihydric phenols are difunctional and their tendency is rather to react with the epoxide resins to form long chain high molecular weight polymerization products with little or no crosslinking.

With trihydric and higher polyhydric phenols, extremely hard and tough products are obtained, not only when equivalent amounts of epoxide resin and trihydric or higher polyhydric phenol are used, but also when much less than the equivalent amount of the phenol is used.

The new compositions of the present invention can be used in the form of their initial admixture of epoxide resin and polyhydric phenol in the form of solutions, or admixed with fillers or pigments, to form paints or varnishes or coating solutions which, on heating, will give insoluble, infusible films; or such compositions can be used in impregnating and laminating and coating wood fibers and other porous or fibrous materials, etc., with resulting heating to convert the product into an infusible, insoluble form.

Paints, enamels, etc. can thus be produced as well as molding mixtures and compositions which, in final form, are infusible, insoluble products.

The new epoxy resin compositions are accordingly valuable for use in making molding compositions and articles as well as for making coating compositions, films, filaments, fibers, adhesives, etc.

One advantage of the compositions is that on final hardening to form insoluble, infusible products, they tend to expand rather than to contract, which is valuable, e.g. in making molded articles where tight fitting molded articles are desired.

This application is a continuation-in-part of my prior application Ser. No. 315,424, filed October 17, 1952, which application is a continuation-in-part of my prior application Ser. No. 250,951, filed October 11, 1951 (Patent No. ,615,008), which application is a continuation in part of my prior applications Ser. No. 189,063 filed October 7, 1950, and Ser. No. 199,932, filed December 8, 1950, now abandoned, which prior applications are continuations-in-part respectively of my prior applications Ser. No. 621,856, filed October 11, 1945, and Ser. No. 617,176, filed September 18, 1945, now abandoned.

I claim:

1. The three-step process of producing insoluble infusible products, which comprises first reacting a dihydric phenol free from reactive groups other than phenolic hydroxyl groups with an excess of a chlorhydrin selected from the class which consists of epichlorhydrin and glycerol dichlorhydrin in the presence of caustic alkali to form a low melting point epoxide resin, admixing with the epoxide resin a dihydric phenol free from reactive groups other than phenolic hydroxyl groups, with the proportion of dihydric phenol to epoxide resin less than that corresponding to the epoxide equivalent of the resin, heating to efiect reaction of the dihydric phenol with said epoxide resin to form a higher molecular weight and higher melting point epoxide resin, and further reacting the resulting resin with a polyhydric phenol containing only aromatic nuclei and having more than two phenolic hydroxyl groups.

2. The process according to claim 1, in which the polyhydric phenol reacted in the third step of the process is used with a catalyst, the amount of polyhydric phenol being substantially equivalent to the epoxide content of the resin.

3. The process according to claim 1, in which the polyhydric phenol reacted in the third step of the process is a trihydric phenol.

4. The process according to claim 1, in which the polyhydric phenol reacted in the third step of the process is a trihydric phenol and is used with about 1% of an alkaline catalyst.

References Cited in the file of this patent UNITED STATES PATENTS 2,502,145 Greenlee Mar. 28, 1950 2,521,911 Greenlee Sept. 12, 1950 2,602,075 Carpenter et a1. July 1, 1952 2,615,008 Greenlee Oct. 21, 1952 2,668,807 Greenlee Feb. 9, 1954 

1. THE THREE-STEP PROCESS OF PRODUCING INSOLUBLE INFUSIBLE PRODUCTS, WHICH COMPRISES FIRST REACTING A DIHYDRIC PHENOL FREE FROM REACTIVE GROUPS OTHER THAN PHENOLIC HYDROXYL GROUP WITH AN EXCESS OF A CHLORHYDRIN SELECTED FROM THE CLASS WHICH CONSISTS OF EPICHLORHYDRIN AND GLYCEROL DICHLORHYDRIN IN THE PRESENCE OF CAUSTIC ALKALI TO FORM A LOW MELTING POINT OPOXIDE RESIN, ADMIXING WITH THE EPOXIDE RESIN A DIHYDROC PHENOL FREE FROM REACTIVE GROUPS OTHER THAN PHENOLIC HYDROXYL GROUPS, WITH THE PORPORTION OF DIHYDRIC PHENOL TO EPOXIDE RESIN LESS THAN THAT CORRESPONDING TO THE EPOXIDE EQUIVALENT OF THE RESIN HEATING TO EFFECT REACTION OF THE DIHYDRIC PHENOL WITH SAID EPOXIDE RESIN TO FROM A HIGHER MOLECULAR WEIGHT AND HIGHER MELTING POINT EPOXIDE RESIN, AND FURTHER REACTING THE RESULTING RESIN WITH A POLYHYDRIC PHENOL CONTAINING ONLY AROMTIC NUCLEI AND HAVING MORE THAN TWO PHENOLIC HYDROXYL GROUPS. 